Hydrocyclone separators are known to be useful for the classification or fractionation of coarse from fine solids suspended in a liquid. In general, a hydrocyclone is an enclosed vertical machine usually comprising a short cylindrical section (head portion) followed by a (conical) tapered section. Feed of a suspension of solids is supplied under predetermined pressure tangentially or in a volute path into the head portion so as to create therein a swirling stream of fluid, which stream follows a path of gradually decreasing radius toward the point of the narrowest radius of the cone, commonly known as the apex.
As the spiral path approaches the apex of the hydrocyclone, a portion of it turns and begins to flow towards the opposite end, i.e. towards the cylindrical section. Also this flow is in a spiral path of radius smaller than the radius of the first spiral while rotating in the same direction. Thus a vortex is generated within the hydrocyclone. The pressure will be lower along the central axis of the vortex and increase radially outwardly. The idea is that the hydrocyclone will separate the particles of the slurry according to shape, size and specific gravity with faster settling particles moving towards the outer wall of the hydrocyclone eventually leaving the hydrocyclone through the apex discharge port. Slower settling particles will move towards the central axis and travel towards the head portion, eventually leaving the hydrocyclone through the overflow discharge tube. The discharge tube is normally extending down into the cylindrical section such that short circuiting of the feed is prevented.
The efficiency of this operation, that is the sharpness of the separation of the coarser from the finer particles, depends on various factors, such as e.g. the size of the apex opening, the feed speed, and the density of the material to be separated and classified. Also the length of the conical section from the cylindrical part to the apex opening will have an impact on the operation of the separation and/or classification.
This separation according to shape, size and specific gravity is sometimes referred to as “stratification”. However, this stratification of the material is not always fully achieved thus causing incomplete classification. Further, the apex opening has a tendency to get clogged during operation, particularly when the separation of particles is rather efficient which results in a very sluggish or dense mass being pushed through the apex opening, and there may be a need to prevent or elevate any such condition.
Thus, there is still a need for improvements in this technical field, and more specifically there is a need for a hydrocyclone separator which provides for good separation but at the same time reduces the risk of the apex getting clogged during operation.